libs: decoder: vc1: implement reset() callback
libs: decoder: vc1: implement reset() callback

remove destroy() and create() callbacks

use g_clear_pointer for rbdu_buffer

no cast for enum

https://bugzilla.gnome.org/show_bug.cgi?id=796308

GStreamer/gstreamer-vaapi,ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi,ceyusa/gstreamer-vaapi